The present invention relates to the wavelength selectivity of lasers.
A desired characteristic of laser operation is per se based on its potential degree of wavelength selectivity. However, in many instances the laser medium such as a plasma is capable of concurrent lasing actions at different wavelengths and will, in fact, do so, so that the output is a multiple of monochromatic beams having different wavelengths. The laser is said to have and to operate at different axial modes of its resonator. This does not necessarily render the laser polychromatic as the various laser modes may be situated within the same spectral line of the optical gain medium.
There is a need in various fields of application and for various purposes to have available a source of monochromatic optical beams of particular wavelengths to be produced one at a time with rapid change-over from one wavelength to another one. One of these needs was discovered by me pursuant to a problem involing measuring the optical energy content of a gas dynamic laser by means of a low power probing laser as will be described below.